PCI: dwc: Fix setting error return on MSI DMA mapping failure

When dma_mapping_error() returns error because of no enough memory,
but dw_pcie_host_init() returns success, which will mislead the callers.

Link: https://lore.kernel.org/r/[e-mail]
Fixes: 07940c369a6b ("PCI: dwc: Fix MSI page leakage in suspend/resume")
Signed-off-by: Jianrong Zhang <[e-mail]>
Signed-off-by: Jiantao Zhang <[e-mail]>
Signed-off-by: Lorenzo Pieralisi <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>

drivers/pci/controller/dwc/pcie-designware-host.c

···
 						      sizeof(pp->msi_msg),
 						      DMA_FROM_DEVICE,
 						      DMA_ATTR_SKIP_CPU_SYNC);
-			if (dma_mapping_error(pci->dev, pp->msi_data)) {
+			ret = dma_mapping_error(pci->dev, pp->msi_data);
+			if (ret) {
 				dev_err(pci->dev, "Failed to map MSI data\n");
 				pp->msi_data = 0;
 				goto err_free_msi;